Technical Field
The present invention relates to a package substrate, especially relates to a package substrate with double sided fine line redistribution layer (RDL) for a system in package. The top side of the package substrate is made adaptive to mount at least one chip thereon. The bottom side of the package substrate is made adaptive to mount at least one chip thereon. The line width of a metal circuit of the middle redistribution layer is wider than a line width of a metal circuit of the top redistribution layer, and the line width of a metal circuit of the middle redistribution layer is wider than a line width of a metal circuit of the bottom redistribution layer.
Description of Related Art
FIG. 1 shows a prior art.
FIG. 1 shows that a first chip 501 and a second chip 502 are configured on a top side of an interposer 51. The interposer 51 is configured on a top side of a package substrate 52. The package substrate 52 is configured on a system board 53. For signal communication between the first chip 501 and the second chip 502, a long path needs to go as indicated by the dash line 55. Referring to FIG. 1, the communication path from chip 501 to chip 502 goes from the circuitry of the interposer 51, package substrate 52, system board 53, back to the package substrate 52, the interposer 51, and then reaches chip 502. The disadvantage for the prior art is that the longer the path it goes, the weaker the signal is received. For a long time, a shorter circuitry for signal communication between neighboring chips is pursued.